1. Field of the Invention
This invention relates generally to systems for color matching and, more particularly, to systems for analyzing and matching tooth shades. Such systems are of particular use in manufacturing dental prosthetics (e.g., crowns, bridges, veneers, and prosthetic teeth) to repair, replace or alter natural teeth, in various dental tooth whitening procedures and to enable communication between patient, dentist and lab technician concerning such procedures.
2. Description of the Related Art
Dentists often repair or replace a diseased, damaged, or unsightly natural tooth of a patient with a crown, bridge, veneer, or prosthetic tooth. One obvious goal in performing such a repair or replacement is to provide the patient with a natural-looking smile despite the presence of the prosthesis. Attempts to reach this goal generally involve matching the color of the prosthesis to the color of the natural tooth being repaired or replaced, and to the colors of the natural teeth that are adjacent where the prosthesis will be placed.
Similarly, dentists often perform various tooth whitening procedures on a patient's natural teeth to reverse the effects of aging, coffee drinking, smoking, and similar activities on the patient's dental appearance. The goal in such procedures is also to provide the patient with a natural-looking smile, and attempts to reach this goal also generally involve color matching.
To this end, manufacturers of the various colored porcelains, resins, compomers ceramers or other direct restorative materials conventionally used in making dental prosthetics, or in repairing discolored, chipped, broken or malformed teeth, typically provide color matching shade guides to dentists which illustrate the various colored porcelains available. As shown in FIG. 1, one such shade guide 10 includes a variety of shade tabs 12, each made of a different colored porcelain available from a manufacturer. A dentist determines the color of a patient's natural teeth by detaching individual shade tabs 12 from the shade guide 10 and holding the shade tabs 12 next to the patient's natural teeth for comparison. Once a color match is found, the dentist orders a dental prosthesis from a dental laboratory in the matching colored porcelain or other material, or, if the patient's teeth are being whitened, the dentist uses the color match as a base against which to compare the eventual results of the whitening process.
This somewhat rudimentary method often provides less than desirable results because of the inaccuracy inherent in the dentist "eyeballing" the color match. Poor lighting, poor vision, eye fatigue, conflicting ambient colors or even lack of patient cooperation in the process, among other things, can cause the dentist to miss the best match. More importantly, the best match is often a combination of two or more colored porcelains, sometimes from different manufacturers, which is difficult to discern by the human eye.
Accordingly, a variety of mechanical and electronic devices have been devised to aid in matching tooth shades. Some of these devices are described in U.S. Pat. No. 5,759,030 to Jung et al., U.S. Pat. No. 5,690,486 to Zigelbaum, U.S. Pat. No. 5,529,492 to Yarovesky et al., U.S. Pat. No. 5,383,020 to Vieillefosse, U.S. Pat. No. 5,055,040 to Clar, U.S. Pat. No. 4,654,794 to O'Brien, and U.S. Pat. No. 4,110,826 to Mollgaard. Unfortunately, none of these devices have been very successful in advancing the tooth shade matching process much beyond the "eyeballing" procedure described above.
Another approach to tooth shade matching is disclosed in JP 4-338465 to Eto, entitled, "Device for Adjusting the Shape and Tone of Prosthetic Teeth". This Japanese patent application discloses a device for adjusting the shape and color tone of prosthetic teeth including a still video camera or a charge coupled device (CCD) camera, an image processor, a video monitor, a printer, and a color tone table. As disclosed in JP 4-338465, a still image is taken of the patient's teeth. The image includes the missing or broken tooth and its symmetrical counterpart. The shape of the symmetrical counterpart is overlaid on the space or location of the missing or broken tooth. The color of the replacement tooth is obtained by color analysis of the remaining teeth on the missing tooth side of the patient's mouth and color tone signals from a digital table stored in advance. The results of the color analysis is a "mix composition" of the individual color tones of color tone adjusting agents for the material that the replacement for the missing tooth is to be constructed. The resulting prosthetic tooth according to JP 4-338465 is a homogenous mix of the individual color tones which may or may not have the appearance of a real tooth, which is usually not homogeneous. JP 4-338465 does not appear to disclose normalizing the digital images or the inclusion of a dental shade standard in the still image to assist in normalizing a digital image. Furthermore, JP 4-338465 does not appear to disclose color analysis of a digital image to obtain a picture of the prosthetic tooth with a map of the tooth shades that are required to match the surrounding teeth.
Yet another approach is disclosed in U.S. Pat. No. 5,766,006 to Murljacic. U.S. Pat. No. 5,766,006 discloses a tooth shade analyzer system and methods including a color CCD camera for capturing an image of a patient's tooth, a shade analyzer subsystem having color processing means for determining the color of the patient's tooth from the color information of the image obtained by the CCD camera, storage means for storing color shade standards, color correlation means for comparing the color of the patient's tooth with the stored shade standards to identify the color of the patient's tooth and means for communicating the color of the patient's tooth to a user of the system. U.S. Pat. No. 5,766,006 requires the same camera be used to capture the image of the patient's tooth and the dental shade standards to avoid having to normalize the color image. U.S. Pat. No. 5,766,006 is thus not capable of using images generated from any source and cannot normalize such arbitrary images using normalization standards. Furthermore, U.S. Pat. No. 5,766,006 does not appear to disclose color analysis of a digital image.
A variation on U.S. Pat. No. 5,766,006 is disclosed in U.S. Pat. No. 5,961,324 to Lehmann which is a continuation-in-part of the application from which U.S. Pat. No. 5,766,006 issued. U.S. Pat. No. 5,961,324 discloses a tooth shade analyzer system and methods including an intraoral camera and a tooth shade analyzer subsystem. The tooth shade analyzer subsystem includes color processing means for determining RGB chromacities of the color image of the patient's tooth and RGB chromacities of the stored tooth shades and means for comparing both. However, U.S. Pat. No. 5,961,324 does not disclose the use of other color models for digital color image analysis, such as hue, saturation, intensity (HSI). Furthermore, U.S. Pat. No. 5,961,324 requires the same camera be used to capture the image of the patient's tooth and the dental shade standards to avoid having to normalize the color image. Thus, the tooth shade analyzer disclosed in U.S. Pat. No. 5,961,324 is not capable of utilizing images generated from any source and cannot normalize such arbitrary images using normalization standards. In addition, U.S. Pat. No. 5,961,324 does not appear to disclose color analyzing the digital image to obtain a picture of the prosthetic tooth with a map of the tooth shades that are required to match the surrounding teeth.
Because of the limitations in the prior art as noted above, there exists a need in the art for a method, apparatus and system for an improved tooth shade matching system that does not require a CCD or other intraoral camera and thus can utilize an image from any source. Furthermore, a need exists in the art for a tooth shade analysis system that does not rely on RGB color models.